docs: def get_transformation(name: str):
      """Get a transformation function and error if its name is not registered.
  
      :param name: The name of a function to look up
      :return: A transformation function
      :raises MissingPipelineFunctionError: If the given function name is not registered
      """
      func = mapped.get(name)
  
      if func is None:
          raise MissingPipelineFunctionError('{} is not registered as a pipeline function'.format(name))
  
      return func